fix(client): strengthen CLOB price read types

[cesarenaldi]

Summary

• return branded DecimalString values from single CLOB price read helpers
• type CLOB batch price maps with TokenId keys: Midpoints, Prices, and Spreads
• preserve partial OrderSide records for fetchPrices results
• add binding runtime coverage, client action/decorator type coverage, integration assertions, and changesets for DEV-416 and DEV-417

Verification

• pnpm lint
• pnpm typecheck
• pnpm test:bindings
• pnpm test:client
• pnpm build

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Note

Medium Risk
Public TypeScript return types change from string and loose records to branded DecimalString and TokenId-keyed maps, which can break downstream consumers at compile time even though runtime parsing behavior is largely unchanged.

Overview
Tightens CLOB price read typings across @polymarket/bindings and @polymarket/client so validated API data is not widened to plain string maps at the boundary.

Bindings: MidpointsSchema, PricesSchema, and SpreadsSchema now key results by TokenId instead of arbitrary strings. Batch fetchPrices shapes are modeled as partial OrderSide → DecimalString records (only requested sides present), with runtime tests for valid parses and rejection of unknown side keys.

Client: Single-token helpers (fetchMidpoint, fetchPrice, fetchSpread) return DecimalString; batch helpers return Midpoints, Prices, and Spreads. The DataActions decorator surface matches those types. New compile-time tests lock the public API; integration tests assert token-keyed batch results and that unrequested sell sides stay absent on fetchPrices.

Patch changesets cover DEV-416 (branded decimals) and DEV-417 (token-keyed batch maps).

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